diff --git a/src/xdiff/README.txt b/src/xdiff/README.txt
index 9e01a3c..3302abc 100644
--- a/src/xdiff/README.txt
+++ b/src/xdiff/README.txt
@@ -1,6 +1,6 @@
 The files in this directory come from the xdiff implementation in git.
 You can find it here: https://github.com/git/git/tree/master/xdiff
-The files were last updated August 31, 2021 from git release v.2.33.0
+The files were last updated March 17, 2023 from git release v.2.40.0
 
 This is originally based on libxdiff, which can be found here:
 http://www.xmailserver.org/xdiff-lib.html
diff --git a/src/xdiff/xdiff.h b/src/xdiff/xdiff.h
index 3994f66..a9169d3 100644
--- a/src/xdiff/xdiff.h
+++ b/src/xdiff/xdiff.h
@@ -66,6 +66,7 @@
 
 /* merge output styles */
 #define XDL_MERGE_DIFF3 1
+#define XDL_MERGE_ZEALOUS_DIFF3 2
 
 typedef struct s_mmfile {
 	char *ptr;
@@ -126,6 +127,7 @@
 #endif
 
 #define xdl_malloc(x) lalloc((x), TRUE)
+#define xdl_calloc(n, sz) lalloc_clear(n*sz, TRUE)
 #define xdl_free(ptr) vim_free(ptr)
 #define xdl_realloc(ptr,x) vim_realloc((ptr),(x))
 
diff --git a/src/xdiff/xdiffi.c b/src/xdiff/xdiffi.c
index cfcbb5d..5a6f0cd 100644
--- a/src/xdiff/xdiffi.c
+++ b/src/xdiff/xdiffi.c
@@ -315,16 +315,19 @@
 	long *kvd, *kvdf, *kvdb;
 	xdalgoenv_t xenv;
 	diffdata_t dd1, dd2;
+	int res;
 
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF)
-		return xdl_do_patience_diff(mf1, mf2, xpp, xe);
-
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
-		return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
-
-	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
-
+	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0)
 		return -1;
+
+	if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF) {
+		res = xdl_do_patience_diff(xpp, xe);
+		goto out;
+	}
+
+	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF) {
+		res = xdl_do_histogram_diff(xpp, xe);
+		goto out;
 	}
 
 	/*
@@ -334,7 +337,7 @@
 	 * One is to store the forward path and one to store the backward path.
 	 */
 	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
-	if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
+	if (!XDL_ALLOC_ARRAY(kvd, 2 * ndiags + 2)) {
 
 		xdl_free_env(xe);
 		return -1;
@@ -359,17 +362,15 @@
 	dd2.rchg = xe->xdf2.rchg;
 	dd2.rindex = xe->xdf2.rindex;
 
-	if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
-			 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
-
-		xdl_free(kvd);
-		xdl_free_env(xe);
-		return -1;
-	}
-
+	res = xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
+			   kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0,
+			   &xenv);
 	xdl_free(kvd);
+ out:
+	if (res < 0)
+		xdl_free_env(xe);
 
-	return 0;
+	return res;
 }
 
 
@@ -390,12 +391,9 @@
 }
 
 
-static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)
+static int recs_match(xrecord_t *rec1, xrecord_t *rec2)
 {
-	return (rec1->ha == rec2->ha &&
-		xdl_recmatch(rec1->ptr, rec1->size,
-			     rec2->ptr, rec2->size,
-			     flags));
+	return (rec1->ha == rec2->ha);
 }
 
 /*
@@ -759,10 +757,10 @@
  * following group, expand this group to include it. Return 0 on success or -1
  * if g cannot be slid down.
  */
-static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g, long flags)
+static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->end < xdf->nrec &&
-	    recs_match(xdf->recs[g->start], xdf->recs[g->end], flags)) {
+	    recs_match(xdf->recs[g->start], xdf->recs[g->end])) {
 		xdf->rchg[g->start++] = 0;
 		xdf->rchg[g->end++] = 1;
 
@@ -780,10 +778,10 @@
  * into a previous group, expand this group to include it. Return 0 on success
  * or -1 if g cannot be slid up.
  */
-static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g, long flags)
+static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
 {
 	if (g->start > 0 &&
-	    recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1], flags)) {
+	    recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1])) {
 		xdf->rchg[--g->start] = 1;
 		xdf->rchg[--g->end] = 0;
 
@@ -839,7 +837,7 @@
 			end_matching_other = -1;
 
 			/* Shift the group backward as much as possible: */
-			while (!group_slide_up(xdf, &g, flags))
+			while (!group_slide_up(xdf, &g))
 				if (group_previous(xdfo, &go))
 					xdl_bug("group sync broken sliding up");
 
@@ -854,7 +852,7 @@
 
 			/* Now shift the group forward as far as possible: */
 			while (1) {
-				if (group_slide_down(xdf, &g, flags))
+				if (group_slide_down(xdf, &g))
 					break;
 				if (group_next(xdfo, &go))
 					xdl_bug("group sync broken sliding down");
@@ -881,7 +879,7 @@
 			 * other file that it can align with.
 			 */
 			while (go.end == go.start) {
-				if (group_slide_up(xdf, &g, flags))
+				if (group_slide_up(xdf, &g))
 					xdl_bug("match disappeared");
 				if (group_previous(xdfo, &go))
 					xdl_bug("group sync broken sliding to match");
@@ -924,7 +922,7 @@
 			}
 
 			while (g.end > best_shift) {
-				if (group_slide_up(xdf, &g, flags))
+				if (group_slide_up(xdf, &g))
 					xdl_bug("best shift unreached");
 				if (group_previous(xdfo, &go))
 					xdl_bug("group sync broken sliding to blank line");
diff --git a/src/xdiff/xdiffi.h b/src/xdiff/xdiffi.h
index 8f1c7c8..126c9d8 100644
--- a/src/xdiff/xdiffi.h
+++ b/src/xdiff/xdiffi.h
@@ -56,9 +56,7 @@
 void xdl_free_script(xdchange_t *xscr);
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg);
-int xdl_do_patience_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
-		xdfenv_t *env);
-int xdl_do_histogram_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
-		xdfenv_t *env);
+int xdl_do_patience_diff(xpparam_t const *xpp, xdfenv_t *env);
+int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env);
 
 #endif /* #if !defined(XDIFFI_H) */
diff --git a/src/xdiff/xemit.c b/src/xdiff/xemit.c
index b578e7a..585ca54 100644
--- a/src/xdiff/xemit.c
+++ b/src/xdiff/xemit.c
@@ -65,7 +65,7 @@
 			*xscr = xch;
 	}
 
-	if (*xscr == NULL)
+	if (!*xscr)
 		return NULL;
 
 	lxch = *xscr;
@@ -96,7 +96,7 @@
 
 
 #if 0
-static long def_ff(const char *rec, long len, char *buf, long sz, void *priv UNUSED)
+static long def_ff(const char *rec, long len, char *buf, long sz)
 {
 	if (len > 0 &&
 			(isalpha((unsigned char)*rec) || /* identifier? */
@@ -120,7 +120,7 @@
 	const char *rec;
 	long len = xdl_get_rec(xdf, ri, &rec);
 	if (!xecfg->find_func)
-		return def_ff(rec, len, buf, sz, xecfg->find_func_priv);
+		return def_ff(rec, len, buf, sz);
 	return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
 }
 #endif
diff --git a/src/xdiff/xhistogram.c b/src/xdiff/xhistogram.c
index 8598a85..c0e3275 100644
--- a/src/xdiff/xhistogram.c
+++ b/src/xdiff/xhistogram.c
@@ -88,19 +88,14 @@
 #define REC(env, s, l) \
 	(env->xdf##s.recs[l - 1])
 
-static int cmp_recs(xpparam_t const *xpp,
-	xrecord_t *r1, xrecord_t *r2)
+static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
 {
-	return r1->ha == r2->ha &&
-		xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
-			    xpp->flags);
+	return r1->ha == r2->ha;
+
 }
 
-#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
-	(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
-
 #define CMP(i, s1, l1, s2, l2) \
-	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
+	(cmp_recs(REC(i->env, s1, l1), REC(i->env, s2, l2)))
 
 #define TABLE_HASH(index, side, line) \
 	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
@@ -256,7 +251,7 @@
 		    int line1, int count1, int line2, int count2)
 {
 	int b_ptr;
-	int sz, ret = -1;
+	int ret = -1;
 	struct histindex index;
 
 	memset(&index, 0, sizeof(index));
@@ -270,23 +265,16 @@
 	index.rcha.head = NULL;
 
 	index.table_bits = xdl_hashbits(count1);
-	sz = index.records_size = 1 << index.table_bits;
-	sz *= sizeof(struct record *);
-	if (!(index.records = (struct record **) xdl_malloc(sz)))
+	index.records_size = 1 << index.table_bits;
+	if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
 		goto cleanup;
-	memset(index.records, 0, sz);
 
-	sz = index.line_map_size = count1;
-	sz *= sizeof(struct record *);
-	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
+	index.line_map_size = count1;
+	if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
 		goto cleanup;
-	memset(index.line_map, 0, sz);
 
-	sz = index.line_map_size;
-	sz *= sizeof(unsigned int);
-	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
+	if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
 		goto cleanup;
-	memset(index.next_ptrs, 0, sz);
 
 	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
 	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
@@ -374,12 +362,8 @@
 	return result;
 }
 
-int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
-	xpparam_t const *xpp, xdfenv_t *env)
+int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env)
 {
-	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
-		return -1;
-
 	return histogram_diff(xpp, env,
 		env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
 		env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
diff --git a/src/xdiff/xmacros.h b/src/xdiff/xmacros.h
index 2809a28..8487bb3 100644
--- a/src/xdiff/xmacros.h
+++ b/src/xdiff/xmacros.h
@@ -34,7 +34,6 @@
 #define XDL_ADDBITS(v,b)	((v) + ((v) >> (b)))
 #define XDL_MASKBITS(b)		((1UL << (b)) - 1)
 #define XDL_HASHLONG(v,b)	(XDL_ADDBITS((unsigned long)(v), b) & XDL_MASKBITS(b))
-#define XDL_PTRFREE(p) do { if (p) { xdl_free(p); (p) = NULL; } } while (0)
 #define XDL_LE32_PUT(p, v) \
 do { \
 	unsigned char *__p = (unsigned char *) (p); \
@@ -50,5 +49,23 @@
 		((unsigned long) __p[2]) << 16 | ((unsigned long) __p[3]) << 24; \
 } while (0)
 
+/* Allocate an array of nr elements, returns NULL on failure */
+#define XDL_ALLOC_ARRAY(p, nr)				\
+	((p) = SIZE_MAX / sizeof(*(p)) >= (size_t)(nr)	\
+		? xdl_malloc((nr) * sizeof(*(p)))	\
+		: NULL)
+
+/* Allocate an array of nr zeroed out elements, returns NULL on failure */
+#define XDL_CALLOC_ARRAY(p, nr)	((p) = xdl_calloc(nr, sizeof(*(p))))
+
+/*
+ * Ensure array p can accommodate at least nr elements, growing the
+ * array and updating alloc (which is the number of allocated
+ * elements) as necessary. Frees p and returns -1 on failure, returns
+ * 0 on success
+ */
+#define XDL_ALLOC_GROW(p, nr, alloc)	\
+	(-!((nr) <= (alloc) ||		\
+	    ((p) = xdl_alloc_grow_helper((p), (nr), &(alloc), sizeof(*(p))))))
 
 #endif /* #if !defined(XMACROS_H) */
diff --git a/src/xdiff/xpatience.c b/src/xdiff/xpatience.c
index f78c897..894a1ba 100644
--- a/src/xdiff/xpatience.c
+++ b/src/xdiff/xpatience.c
@@ -69,7 +69,6 @@
 	} *entries, *first, *last;
 	/* were common records found? */
 	unsigned long has_matches;
-	mmfile_t *file1, *file2;
 	xdfenv_t *env;
 	xpparam_t const *xpp;
 };
@@ -139,23 +138,17 @@
  *
  * It is assumed that env has been prepared using xdl_prepare().
  */
-static int fill_hashmap(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
+static int fill_hashmap(xpparam_t const *xpp, xdfenv_t *env,
 		struct hashmap *result,
 		int line1, int count1, int line2, int count2)
 {
-	result->file1 = file1;
-	result->file2 = file2;
 	result->xpp = xpp;
 	result->env = env;
 
 	/* We know exactly how large we want the hash map */
 	result->alloc = count1 * 2;
-	result->entries = (struct entry *)
-		xdl_malloc(result->alloc * sizeof(struct entry));
-	if (!result->entries)
+	if (!XDL_CALLOC_ARRAY(result->entries, result->alloc))
 		return -1;
-	memset(result->entries, 0, result->alloc * sizeof(struct entry));
 
 	/* First, fill with entries from the first file */
 	while (count1--)
@@ -198,9 +191,9 @@
  * item per sequence length: the sequence with the smallest last
  * element (in terms of line2).
  */
-static struct entry *find_longest_common_sequence(struct hashmap *map)
+static int find_longest_common_sequence(struct hashmap *map, struct entry **res)
 {
-	struct entry **sequence = xdl_malloc(map->nr * sizeof(struct entry *));
+	struct entry **sequence;
 	int longest = 0, i;
 	struct entry *entry;
 
@@ -211,9 +204,8 @@
 	 */
 	int anchor_i = -1;
 
-	// Added to silence Coverity.
-	if (sequence == NULL)
-		return map->first;
+	if (!XDL_ALLOC_ARRAY(sequence, map->nr))
+		return -1;
 
 	for (entry = map->first; entry; entry = entry->next) {
 		if (!entry->line2 || entry->line2 == NON_UNIQUE)
@@ -234,8 +226,9 @@
 
 	/* No common unique lines were found */
 	if (!longest) {
+		*res = NULL;
 		xdl_free(sequence);
-		return NULL;
+		return 0;
 	}
 
 	/* Iterate starting at the last element, adjusting the "next" members */
@@ -245,8 +238,9 @@
 		entry->previous->next = entry;
 		entry = entry->previous;
 	}
+	*res = entry;
 	xdl_free(sequence);
-	return entry;
+	return 0;
 }
 
 static int match(struct hashmap *map, int line1, int line2)
@@ -256,8 +250,7 @@
 	return record1->ha == record2->ha;
 }
 
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
+static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 		int line1, int count1, int line2, int count2);
 
 static int walk_common_sequence(struct hashmap *map, struct entry *first,
@@ -288,8 +281,7 @@
 
 		/* Recurse */
 		if (next1 > line1 || next2 > line2) {
-			if (patience_diff(map->file1, map->file2,
-					map->xpp, map->env,
+			if (patience_diff(map->xpp, map->env,
 					line1, next1 - line1,
 					line2, next2 - line2))
 				return -1;
@@ -328,8 +320,7 @@
  *
  * This function assumes that env was prepared with xdl_prepare_env().
  */
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
+static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
 		int line1, int count1, int line2, int count2)
 {
 	struct hashmap map;
@@ -348,7 +339,7 @@
 	}
 
 	memset(&map, 0, sizeof(map));
-	if (fill_hashmap(file1, file2, xpp, env, &map,
+	if (fill_hashmap(xpp, env, &map,
 			line1, count1, line2, count2))
 		return -1;
 
@@ -362,25 +353,21 @@
 		return 0;
 	}
 
-	first = find_longest_common_sequence(&map);
+	result = find_longest_common_sequence(&map, &first);
+	if (result)
+		goto out;
 	if (first)
 		result = walk_common_sequence(&map, first,
 			line1, count1, line2, count2);
 	else
 		result = fall_back_to_classic_diff(&map,
 			line1, count1, line2, count2);
-
+ out:
 	xdl_free(map.entries);
 	return result;
 }
 
-int xdl_do_patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env)
+int xdl_do_patience_diff(xpparam_t const *xpp, xdfenv_t *env)
 {
-	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
-		return -1;
-
-	/* environment is cleaned up in xdl_diff() */
-	return patience_diff(file1, file2, xpp, env,
-			1, env->xdf1.nrec, 1, env->xdf2.nrec);
+	return patience_diff(xpp, env, 1, env->xdf1.nrec, 1, env->xdf2.nrec);
 }
diff --git a/src/xdiff/xprepare.c b/src/xdiff/xprepare.c
index abeb8fb..c84549f 100644
--- a/src/xdiff/xprepare.c
+++ b/src/xdiff/xprepare.c
@@ -78,15 +78,14 @@
 
 		return -1;
 	}
-	if (!(cf->rchash = (xdlclass_t **) xdl_malloc(cf->hsize * sizeof(xdlclass_t *)))) {
+	if (!XDL_CALLOC_ARRAY(cf->rchash, cf->hsize)) {
 
 		xdl_cha_free(&cf->ncha);
 		return -1;
 	}
-	memset(cf->rchash, 0, cf->hsize * sizeof(xdlclass_t *));
 
 	cf->alloc = size;
-	if (!(cf->rcrecs = (xdlclass_t **) xdl_malloc(cf->alloc * sizeof(xdlclass_t *)))) {
+	if (!XDL_ALLOC_ARRAY(cf->rcrecs, cf->alloc)) {
 
 		xdl_free(cf->rchash);
 		xdl_cha_free(&cf->ncha);
@@ -112,7 +111,6 @@
 	long hi;
 	char const *line;
 	xdlclass_t *rcrec;
-	xdlclass_t **rcrecs;
 
 	line = rec->ptr;
 	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
@@ -128,14 +126,8 @@
 			return -1;
 		}
 		rcrec->idx = cf->count++;
-		if (cf->count > cf->alloc) {
-			cf->alloc *= 2;
-			if (!(rcrecs = (xdlclass_t **) xdl_realloc(cf->rcrecs, cf->alloc * sizeof(xdlclass_t *)))) {
-
+		if (XDL_ALLOC_GROW(cf->rcrecs, cf->count, cf->alloc))
 				return -1;
-			}
-			cf->rcrecs = rcrecs;
-		}
 		cf->rcrecs[rcrec->idx] = rcrec;
 		rcrec->line = line;
 		rcrec->size = rec->size;
@@ -164,7 +156,7 @@
 	unsigned long hav;
 	char const *blk, *cur, *top, *prev;
 	xrecord_t *crec;
-	xrecord_t **recs, **rrecs;
+	xrecord_t **recs;
 	xrecord_t **rhash;
 	unsigned long *ha;
 	char *rchg;
@@ -178,51 +170,42 @@
 
 	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
 		goto abort;
-	if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))
+	if (!XDL_ALLOC_ARRAY(recs, narec))
 		goto abort;
 
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
-		hbits = hsize = 0;
-	else {
-		hbits = xdl_hashbits((unsigned int) narec);
-		hsize = 1 << hbits;
-		if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
-			goto abort;
-		memset(rhash, 0, hsize * sizeof(xrecord_t *));
-	}
+	hbits = xdl_hashbits((unsigned int) narec);
+	hsize = 1 << hbits;
+	if (!XDL_CALLOC_ARRAY(rhash, hsize))
+		goto abort;
 
 	nrec = 0;
-	if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
+	if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
 		for (top = blk + bsize; cur < top; ) {
 			prev = cur;
 			hav = xdl_hash_record(&cur, top, xpp->flags);
-			if (nrec >= narec) {
-				narec *= 2;
-				if (!(rrecs = (xrecord_t **) xdl_realloc(recs, narec * sizeof(xrecord_t *))))
-					goto abort;
-				recs = rrecs;
-			}
+			if (XDL_ALLOC_GROW(recs, nrec + 1, narec))
+				goto abort;
 			if (!(crec = xdl_cha_alloc(&xdf->rcha)))
 				goto abort;
 			crec->ptr = prev;
 			crec->size = (long) (cur - prev);
 			crec->ha = hav;
 			recs[nrec++] = crec;
-
-			if ((XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
-			    xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
+			if (xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
 				goto abort;
 		}
 	}
 
-	if (!(rchg = (char *) xdl_malloc((nrec + 2) * sizeof(char))))
+	if (!XDL_CALLOC_ARRAY(rchg, nrec + 2))
 		goto abort;
-	memset(rchg, 0, (nrec + 2) * sizeof(char));
 
-	if (!(rindex = (long *) xdl_malloc((nrec + 1) * sizeof(long))))
-		goto abort;
-	if (!(ha = (unsigned long *) xdl_malloc((nrec + 1) * sizeof(unsigned long))))
-		goto abort;
+	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
+	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
+		if (!XDL_ALLOC_ARRAY(rindex, nrec + 1))
+			goto abort;
+		if (!XDL_ALLOC_ARRAY(ha, nrec + 1))
+			goto abort;
+	}
 
 	xdf->nrec = nrec;
 	xdf->recs = recs;
@@ -279,8 +262,7 @@
 	enl1 = xdl_guess_lines(mf1, sample) + 1;
 	enl2 = xdl_guess_lines(mf2, sample) + 1;
 
-	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF &&
-	    xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
+	if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
 		return -1;
 
 	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
@@ -305,8 +287,7 @@
 		return -1;
 	}
 
-	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)
-		xdl_free_classifier(&cf);
+	xdl_free_classifier(&cf);
 
 	return 0;
 }
@@ -388,11 +369,8 @@
 	xdlclass_t *rcrec;
 	char *dis, *dis1, *dis2;
 
-	if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {
-
+	if (!XDL_CALLOC_ARRAY(dis, xdf1->nrec + xdf2->nrec + 2))
 		return -1;
-	}
-	memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);
 	dis1 = dis;
 	dis2 = dis1 + xdf1->nrec + 1;
 
diff --git a/src/xdiff/xutils.c b/src/xdiff/xutils.c
index f13a854..a4370e6 100644
--- a/src/xdiff/xutils.c
+++ b/src/xdiff/xutils.c
@@ -122,7 +122,7 @@
 	long nl = 0, size, tsize = 0;
 	char const *data, *cur, *top;
 
-	if ((cur = data = xdl_mmfile_first(mf, &size)) != NULL) {
+	if ((cur = data = xdl_mmfile_first(mf, &size))) {
 		for (top = data + size; nl < sample && cur < top; ) {
 			nl++;
 			if (!(cur = memchr(cur, '\n', top - cur)))
@@ -432,3 +432,20 @@
 
 	return 0;
 }
+
+void* xdl_alloc_grow_helper(void *p, long nr, long *alloc, size_t size)
+{
+	void *tmp = NULL;
+	size_t n = ((LONG_MAX - 16) / 2 >= *alloc) ? 2 * *alloc + 16 : LONG_MAX;
+	if (nr > (long)n)
+		n = nr;
+	if (SIZE_MAX / size >= n)
+		tmp = xdl_realloc(p, n * size);
+	if (tmp) {
+		*alloc = n;
+	} else {
+		xdl_free(p);
+		*alloc = 0;
+	}
+	return tmp;
+}
diff --git a/src/xdiff/xutils.h b/src/xdiff/xutils.h
index fba7bae..fd0bba9 100644
--- a/src/xdiff/xutils.h
+++ b/src/xdiff/xutils.h
@@ -42,6 +42,7 @@
 int xdl_fall_back_diff(xdfenv_t *diff_env, xpparam_t const *xpp,
 		       int line1, int count1, int line2, int count2);
 
-
+/* Do not call this function, use XDL_ALLOC_GROW instead */
+void* xdl_alloc_grow_helper(void* p, long nr, long* alloc, size_t size);
 
 #endif /* #if !defined(XUTILS_H) */